Super single tires, which are wide base low aspect ratio truck tires replacing two small base tires, so-called dual mounted tires, have been used for years on trailers. Such tires are usually of size 385/65R22.5 or 385/55R22.5 and have a maximum load-carrying capacity of 4.5 metric tons.
Over the years these wide base tires appeared more and more on trucks in the steering position because they had an expected higher mileage.
It has become of interest to use also super single tires in the drive positions.
Tires in the drive position have to bear a part of the trailer load and must have an increased load capacity. Tire standards define a load capacity of 5.8 metric tons and a maximum speed of 110 km/h. These tires have very low aspect ratios and are usually of size 495/45R22.5. Drive tires are exposed to harsh service conditions and conventional constructions show crown area durability problems. Furthermore, the pressure distribution through the elastomeric blocks in the footprint lacks the required uniformity.
U.S. Pat. No. 6,401,778 B1 discloses a pneumatic truck tire having a radial carcass reinforcement and two working crown plies of inextensible reinforcing elements. An additional ply essentially parallel to the circumferential direction of the tire is positioned between the two working plies. Both working plies extend axially beyond the axial width of the additional ply and are coupled with each other over an axial length of at least 16% of the maximum axial width of the carcass reinforcement. This tire design may constitute an improvement with regard to earlier truck tires. However, durability and footprint shape leave still room for improvements.
US 2005/0126674 A1 discloses another pneumatic truck tire, in particular a super single radial truck tire. The tire comprises a crown reinforcing structure including a single helically wound belt ply reinforced with high elongation steel cords. In one embodiment of this publication, the tire comprises four belts on top of two steel strips. The strips are located between the carcass ply and the radially inner helically wound ply. In practice, said tire may show groove cracking at the intermediate shoulder groove resulting in an unsatisfactory durability. Furthermore, breaker edge separation between the radially outer breakers may occur under heavy duty resulting as well in an unfavorable durability and/or stability. Moreover, the footprint shape of said tire may still be improved. At last, the described tire may show an increased shoulder wear decreasing the performance of the tire.